A screw eye is a fastener that consist of a threaded shank and a circular ring. You must understands the dimensions of a screw eye so that you can select the correct screw eye for your spesific project. The shank diameter is the thickness of the threaded part of the screw eye, and the shank diameter determine how much pullout strength the screw eye will provide.
The inner diameter is the space inside a circular ring of the screw eye, and the inner diameter determines whether a rope or a hook will fit through the screw eye. If the inner diameter is too small, the rope or hook will not fit through the inner diameter, and if the outer diameter is too large, you will not be able to place screw eye close together. You must match the size of the screw eye to the weight of the objects that you want to hang.
How to Choose and Install a Screw Eye
The weight of the object determines the working load limit that you need from a screw eye. The working load limit is the maximum amount of weight that a screw eye can safely support under normal condition. For example, a small screw eye may be sufficent for a picture wire, but a small screw eye isnt sufficent for a heavy hammock because a small screw eye dont have a high enough working load limit.
You should always choose a screw eye that has a working load limit that is equal or greater than the weight of the object you are hanging. The material of the screw eye is an important factor because the material of the screw eye determine how the screw eye reacts to the environment. Zinc-plated steel screw eyes are suitable for use in indoor environments where there is no moisture.
However, zinc-plated steel screw eyes will rust if you use them in outdoor environment. If you are working in a coastal environment, you should use stainless steel screw eyes because stainless steel screw eyes resists salt air. For heavy duty outdoor structures, you should use hot-dip galvanized screw eyes because hot-dip galvanized screw eyes can withstand the elements for a long time.
You must drill a pilot hole before you install a screw eye into wood. Wood is a fibrous material, and if you drive a screw eye into wood without a pilot hole, the pressure from the screw eye will cause the wood to split. You should drill a pilot hole that is approximately seventy-five percent of the diameter of the screw eye shank.
A pilot hole that is seventy-five percent of the shank diameter allow the threads of the screw eye to grip the wood without creating enough pressure to crack the wood. The pilot hole must be deep enough to accommodate the threaded portion of the screw eye, but the pilot hole does not need to go through the entire piece of wood. You should install the screw eye carefully to ensure that the screw eye is seated correct.
You should start the installation of the screw eye by hand because starting by hand ensure that the threads of the screw eye are not crossing. You can use a screwdriver or a rod through the circular ring of the screw eye to provide leverage so that you can tighten the screw eye firm. If you are hanging an object that moves, such as a swing, you must account for shock loads.
A shock load is a sudden movement that increases the force on the screw eye, and a shock load can make the force exceed the working load limit of the screw eye. Therefore, you should choose a screw eye with a working load limit that is significantly higher than the static weight of the object if the object will experience shock load.
